Comparative Study of Sawtooth Physics and Alfvén Waves via 2-D ECE Imaging on KSTAR, DIII-D, AUG and TEXTOR

High temporal and spatial resolution 2-D images of the sawtooth crash via the upgraded Electron Cyclotron Emission Imaging (ECEI) system on Toroidal EXperiment for Technology Oriented Research (TEXTOR) tokamak plasmas revealed new information concerning the sawtooth crash process. This includes: 1) observation of a wide range of crash time scales up to the resistive time scale 2) observation of reversal of the toroidal rotation with coinjection tangential-neutral beam. Subsequently, ECEI systems based on the TEXTOR upgraded system have been developed for DIII-D, ASDEX-UPGRADE (AUG) and Korean Superconducting Tokamak Advanced Research (KSTAR) to study various magnetohydrodynamic (MHD) instabilities and Alfven waves. The systems on AUG and DIII-D have already produced exciting new physics. The most sophisticated ECEI system yet has just been installed on KSTAR and will explore variety of MHD physics essential for high beta steady state operation.